Alternating current generator for a car

ABSTRACT

Excitation of a field coil 2 is carried out by a separated power source 9 placed independent of a battery 8 to increase the output of a generator. A solar battery 10, a piezoelectric element 13 or a thermoelectric converting element 19 is used as the separately exciting means so that the output of the generator is increased for an exciting current effected by the separately exciting means.

CROSS REFERENCE TO OTHER APPLICATIONS

Reference is made to co-pending applications of the same inventors asthe present application, namely Ser. Nos. 576,387 and 576,390.

FIELD OF TECHNOLOGY

The present invention relates to an alternating current generator for acar for charging a battery.

BACKGROUND OF TECHNOLOGY

FIG. 1 is a circuit diagram showing an embodiment of the conventionalalternating current generator for a car. In the figure, the referencenuemral 1 designates an armature coil having a three phase connectionfor generating an alternating current output and the numeral 2designates a field coil, these parts constituting a three phasealternating current generator. The reference numeral 3 designates a mainrectifying device for rectifying the alternating current output of thearmature coil 1; the numeral 4 designates an auxiliary rectifying devicefor rectifying the alternating current output of the armature coil 1;the numeral 5 designates a voltage controlling device which turns on andoff an exciting current passing to the field coil 2; the numeral 6designates a key-switch; the numeral 7 designates a charge lampconnected to the key-switch 6 in series; and the numeral 8 designates abattery.

The positive side of the battery 8 charged by the output of the mainrectifying device 3 is connected to the voltage controlling device 5through a serial connection of the key-switch 6, a charge lamp 7 and thefield coil 2. The output of the auxiliary rectifying device 4 is, on onehand, connected to the voltage controlling device 5 and is, on the otherhand, connected to the voltage controlling device 5 through the fieldcoil 2.

The operation of the circuit constructed as above-mentioned will bedescribed.

First of all, when the key-switch 6 is closed, an exciting current ispassed to the field coil 2 through a circuit of the positive (+) side ofbattery 8--key-switch 6--charge lamp 7--field coil 2--voltagecontrolling device 5--negative (-) side of battery 8. After this, whenan engine is actuated for revolution whereby the terminal voltage of thegenerator increases, an exciting current is supplied from the auxiliaryrectifying device 4 to the field coil 2 and the generator starts togenerate power as a self-excited generator.

In such alternating current generator constructed as above-mentioned,however, a part of an output current is consumed as an exciting currentto cause reduction in output from the exciting current corresponding toabout ten percent of the output current of the generator and to causeconsumption of excessive power of the engine disadvantageously.

SUMMARY OF THE INVENTION

In the present invention, an exciting current is supplied from a powersoure other than a battery so as to constitute a generator as aseparately excited generator whereby for instance, ten percent increaseof an output current can be obtained even though the size of thegenerator is the same as the conventional one.

In the present invention, a generator is miniaturized and efficiency ofthe generator is improved by feeding an exciting current for a fieldcoil from a solar battery which does not require power of an engine.

Further, in the present invention, an exciting current for a field coilis obtained by a piezoelectric element for converting vibration of anengine into electrical power so that the vibration of the engine iseffectively utilized to improve efficiency of a generator.

The present invention is further advantageous from the view thatefficiency of a generator can be advantageously improved by utilizingwaste heat discharged from an engine in effective manner, without usingany power of the engine, by providing an exciting means in whichexcitation of a field coil is carried out by a power source for separateexcitation which performs heat-electricity conversion of the waste heatdischarged from the engine so that a generator is used as a separatelyexcited generator.

BRIEF DESCRIPTION OF DRAWING

FIG. 1 is a circuit diagram of the conventional alternating currentgenerator for a car;

FIG. 2 is a circuit diagram of an embodiment of the alternating currentgenerator for a car according to the present invention;

FIG. 3 is a characteristic diagram showing effect of the presentinvention in comparison with the conventional generator;

FIG. 4 is a circuit diagram of another embodiment of the alternatingcurrent generator according to the present invention;

FIG. 5 is a circuit diagram of a still another embodiment of thealternating current generator of the present invention; and

FIG. 6 is a circuit diagram of a separate embodiment of the alternatingcurrent generator of the present invention.

PREFERRED EMBODIMENT OF THE PRESENT INVENTION

FIG. 2 is a circuit diagram showing an embodiment of the presentinvention.

In FIG. 2, the reference numeral 9 designates a power source other thanthe battery 8. The power source can be a second battery or a secondgenerator and so on and one end of the power source is connected to thefield coil 2 and the other end is grounded.

In the embodiment described above, when an engine is started, agenerator initiates generation of power since an exciting current passesthrough the circuit of the power source 9--field coil 2--voltagecontrolling device 5--power source 9. Since the generatorabove-mentioned is so constructed that the exciting current is suppliedfrom the power source 9 other than the battery to act as a separatelyexcited generator, power generation is started earlier than that of theconventional generator for a time corresponding to the exciting currentand an output current also increases for the exciting current.

FIG. 4 shows another embodiment of the present invention.

The reference numeral 10 designates an array of solar batteries; 11designates a switch to detect a voltage produced in the solar batteryarray 10 to perform opening and closing operations; and 12 designates areverse current blocking diode connected in the forward directionbetween the solar battery array 10 and the switch 11.

The junction of the switch 11 and the diode 12 is connected to thevoltage controlling device 5 through the field coil 2 and the positiveside of the battery 8 whose negative side is grounded is connected tothe switch 11 and is also connected to the voltage controlling device 5through the key-switch 6.

The operation of the embodiment shown in FIG. 4 will be described. Incase that a voltage produced by the solar battery array 10 is above apreviously determined value, the switch 11 is opened whereby an excitingcurrent is passed to the field coil 2 through the circuit of the solarbattery array 10--diode 12--field coil 2--voltage controlling device5--solar battery array 10. Then, when an engine is driven with theexciting current passing, the generator starts to generate power as aseparately excited generator.

Thus, the exciting current is supplied to the field coil 2 from thesolar battery array 10 and accordingly, as shown in the characteristiccomparison diagram of FIG. 3 in which the abscissa denotes revolution(rpm) and the ordinate denotes output current A, the revolution at thetime of starting generation of power in the characteristic curve (a) ofthe generator of the present invention is lowered by No(=N₁ -N₂)rpm incomparison with the characteristic curve (b) of the conventionalgenerator and the output current is increased for an amount of the fieldcurrent IF.

In case that sunshine is insufficient as in the condition of night,rainy weather and so on, there is formed a auxiliary circuit in such amanner that an exciting current flows in the field coil 2 through thecircuit having a higher potential of the positive side of battery8--which 11--field coil 2--voltage controlling device 5--the negativeside of battery 8.

In accordance with the embodiment as above-mentioned, an excitingcurrent for a field coil is supplied from a solar battery requiring nopower from an engine with the consequence that there is attainable aremarkable effect such that much output current is obtained incomparison with the conventional generator having the same size, hencesubstantial reduction in size of the generator is achieved andefficiency of the generator is also improved.

FIG. 5 shows still another embodiment of the present invention.

In FIG. 5, the reference numeral 13 designates a piezoelectric elementfor converting vibration at an engine into electricity and thepiezoelectric element is constituted, for instance, by Rochelle salt,quartz and so on. 14 designates a surge absorbing element such as avaristor which is connected in parallel to the piezoelectric element 13to control a voltage produced in the piezoelectric element to be at apredetermined value or lower; 15 designates a capacitor which stores andsmooths electric energy produced in the piezoelectric element 13 tooutput it to the field coil 2 of the generator; 16 and 17 respectivelydesignate reverse current blocking diodes and 18 designates a switch todetect the terminal voltage of the capacitor 15 to perform opening andclosing operations.

One terminal of the piezoelectric element 13 whose other terminal isgrounded is connected to the switch 18 through the diodes 16, 17serially connected in the forward direction. The junction of the diode17 and the switch 18 is connected to the voltage controlling device 5through the field coil 2. The positive side of the battery 8 whosenegative side is grounded is connected to the switch 18 and is alsoconnected to the voltage controlling device 5 through the key-switch 6.

The operation of the embodiment shown in FIG. 5 will be described.

In case that the terminal voltage of the capacitor 15 is below apreviously determined value, the switch 18 is closed whereby an excitingcurrent is passed to the field coil 2 through the circuit of thepositive terminal of battery 8--switch 18--field coil 2--voltagecontrolling device 5--negative terminal of battery 8. Accordingly,actuation of the engine starts generation of power.

Then, when a force is applied to the piezoelectric element 13 throughthe vibration of the engine, electromotive force is produced andelectric current flows into the capacitor 15 through the diode 16whereby the terminal voltage of the capacitor 15 increases. When theterminal voltage of the capacitor reaches the previously determinedvalue, the switch 18 opens to feed the exciting current to the fieldcoil 2 through the circuit of the capacitor 15--diode 17--field coil2--voltage controlling device 5--capacitor 15. Under the conditiondescribed above, revolution of the engine causes the generator to startgeneration of power as a separately excited generator.

Thus, the exciting current is supplied through the piezoelectric element13 and the capacitor 15 and accordingly, as shown in characteristiccomparison diagram of FIG. 3 in which the abscissa denotes revolution(rpm) and the ordinate denotes output current A, the revolution at thetime of starting generation of power in the characteristic curve (a) ofthe embodiment of the present invention is lowered by No(=N₁ -N₂)rpm incomparison with the characteristic curve (b) of the conventionalgenerator and the output current is increased for the exciting currentIF.

In accordance with this embodiment, an exciting current for a field coilis supplied through a piezoelectric element which converts the vibrationof an engine into electricity with the result that there is attainable aremarkable effect such that much output is obtained in comparison withthe conventional generator having the same size, hence substantialreduction in size is achieved and efficiency of the generator is alsoimrpoved.

FIG. 6 is a separate embodiment of the present invention.

In FIG. 6, the reference numeral 19 designates a power source forseparate excitation which performs thermoelectric conversion of heat ofexhaust gas as waste heat of an engine or cooling water for the engine;20 designates a switch to detect a voltage produced in the power sourcefor separate excitation 19 so as to perform opening and closingoperations; 21 designates a reverse current blocking diode connected inthe forward direction between the power source for separate excitation19 and the switch 20.

The junction of the switch 20 and the diode 21 is connected to thevoltage controlling device 5 through the field coil 2. The positive sideof the battery 8 whose negative side is grounded is connected to theswitch 20 and is also connected to the voltage controlling device 5through the key-switch 6.

The operation of the embodiment shown in FIG. 6 will be described.

At the initiation of operation of the engine, there is substantially nowaste heat, hence voltage to be produced by the power source forseparate excitation is zero. Accordingly, an exciting current is passedto the field coil 2 through the circuit of the positive terminal ofbattery 8--switch 20--field coil 2--voltage controlling device5--negative terminal of battery 8 since the switch 20 is in closedstate. Under the condition described above, as temperature of the wasteheat of the engine becomes increasing, the power source for separateexcitation 19 which in generally constituted by thermoelectric metalssuch as iron-Constantan, Chromel-Alumel and so on, being well known as athermocouple or a thermoelectric semiconductor such as PbTe.Ge-Si alloy,produces a thermal electromotive force due to Seebeck effect. When theterminal voltage of the power source for separately excitation rises toreach a previously determined value, the switch 20 is opened. Theopening of the switch 20 passes an exciting current to the field coil 2through the circuit of the positive terminal of power source forseparate excitation 19--diode 21--field coil 2--voltage controllingdevice 5--negative terminal of power source for separate excitation 19.Then, when the engine is driven, the generator starts generation ofpower as a separately excited generator.

Thus, the exciting current is supplied through the power source forseparate excitation 19 and accordingly, as shown in characteristiccomparison diagram of FIG. 3 in which the abscissa denotes revolution(rpm) and the ordinate denotes output current A, the revolution at thetime of starting generation of power in the characteristic curve (a) ofthe embodiment of the present invention is lowered by No(=N₁ -N₂)rpm incomparison with the characteristic curve (b) of the conventionalgenerator and the output current is increased for the exciting currentIF.

In this embodiment, description has been made as to use of thethermoelectric metals or the thermoelectric semiconductor as athermoelectric converting element of the power source for separateexcitation 19. The present invention is not limited to use of theseelements but it is possible to use a thermionic generator utilizingphenomenon that thermoelectrons are emitted by heating metal beyond acertain temperature or Rochelle salt generating a thermal electromotiveforce based on pyroelectric effect to obtain the same effect asdescribed in the above-mentioned embodiment.

In accordance with the embodiment of the present invention, an excitingcurrent for a field coil is supplied from a power source for separateexcitation which does not require any power of an engine andaccordingly, there is attainable a remarkable effect such that muchoutput current is obtained in comparison with the conventional generatorhaving the same size, hence substantial reduction in size of thegenerator is achieved and efficiency of the generator is also improved.

INDUSTRIAL UTILITY

The present invention is applicable not only to an alternating currentgenerator for a vehicle but also to a car such as a farm tractor, anindustrial vehicle and so on.

We claim:
 1. An alternating current system for a car, comprising:a fieldcoil; an armature coil having a three-phase connection to generate analternating current output; a rectifying device for rectifying thealternating current output; a battery to be charged with the output ofsaid rectifying device; a voltage controlling device for turning on andoff the field current passing to said field coil; and a power sourceseparate from said battery and separate from said rectifying device forsupplying said field current; wherein said field current is suppliedseparately from said rectified output, so as to produce an increasedrectified output.
 2. An alternating current system according to claim 1,wherein said power source is constituted by a solar battery.
 3. Analternating current system for a car according to claim 1, wherein saidpower source is constituted by a piezoelectric element converting thevibration of an engine into electrical energy.
 4. An alternating currentsystem for a car according to claim 1, wherein said power source isconstituted by a piezoelectric element for converting the vibration ofan engine into electrical energy and a surge absorbing element and acapacitor which are respectively connected in parallel to saidpiezoelectric element.
 5. An alternating current system for a caraccording to claim 4, wherein said piezoelectric element is formed byRochelle salt and said surge absorbing element is a varistor.
 6. Analternating current system for a car according to claim 1, wherein saidpower source is formed by a power source performing heat-electricityconversion of waste heat discharged from an engine.
 7. An alternatingcurrent system for a car according to claim 6, wherein said power sourceperforming heat-electricity conversion of the waste heat discharged fromthe engine is a thermocouple of iron-Constantan.
 8. An alternatingcurrent system for a car according to claim 6, wherein said power sourceperforming heat-electricity conversion of the waste heat discharged fromthe engine is formed by a thermoelectric semiconductor.
 9. Analternating current system for a car, comprising:a field coil; anarmature coil having a three-phase connection to generate an alternatingcurrent output; a rectifying device for rectifying the alternatingcurrent output; a battery to be charged with the output of saidrectifying device; a voltage controlling device for turning on and offthe field current passing to said field coil; a power source separatefrom said battery for supplying said field current; and a switchconnected between said power source and said battery for comparing thevoltage from said power source to a threshold value and supplying saidfield current from said battery when said voltage is below the thresholdvalue and supplying said field current from said power source when saidvoltage is above said threshold value; wherein said field current issupplied separately from said rectified output when the voltage fromsaid power source is sufficiently large, so as to produce an increasedrectified output.